Dryer fire detection, prevention, and suppression system

ABSTRACT

Described herein is a system for detecting, preventing, and suppressing dryer fires using temperature probes coupled to an alarm system, air flow monitoring, and localized fire suppression. The components of the system are positioned and integrated with each other to prevent and, if necessary, detect and suppress localized fires that may occur in commercial or residential fabric drying machines (i.e., dryers).

FIELD OF THE DISCLOSURE

This disclosure relates to a system for detecting, preventing, and suppressing fires in fabric-drying machines.

BACKGROUND

U.S. fire departments respond to an estimated average of 14,692 home structure fires involving clothes dryers annually. On average these fires cause 9 deaths, 444 injuries, and $238 million dollars in property damage each year according to the National Fire Protection Association. Additionally, scientists at Worcester Polytechnical Institute have studied the environmental impacts of such fires on air pollution, water contamination, and release of toxic substances. A need exists, therefore, for ways to prevent fires from occurring or growing sufficiently large to cause damage.

SUMMARY OF THE DISCLOSURE

Aspects include a system having a dryer, a temperature sensor positioned to measure the temperature inside the dryer or associated ductwork wherein the temperature sensor is coupled to an alarm system; an air flow sensor positioned to measure the air flow from the dryer or through associated ductwork; and a fire suppression system positioned to suppress fires within the dryer or associated ductwork. In some aspects, the system has more than one temperature sensor coupled to the alarm system.

In some aspects, the alarm system is integrated with the dryer, whereas in other aspects the alarm system is separate from the dryer device.

In some aspects, the alarm system includes an audible alarm, a visible alarm, or both. In some aspects, the alarm system includes a wired or wireless data communications transmitter and/or receiver. In some aspects the alarm system is coupled to the dryer heat source.

In some aspects, the air flow sensor is coupled to the alarm system.

In some aspects, the fire suppression system is a powder fire suppression system, inert gas fire suppression system, or fluid-based fire suppression system. In some aspects, the fire suppression system is a powder fire suppression system. In some aspects, the fire suppression system is passively triggered. In some aspects, the fire suppression system further includes a sensor.

DETAILED DESCRIPTION

Described herein is a system for detecting, preventing, and suppressing fires that occur in machines used to dry fabrics and other goods, such as household clothes dryers. The system accomplishes this goal by using sensors, monitoring devices, alarms, and other notifications to detect the conditions that can lead to fires before the fires form. The system also extinguishes fires that occur at their source to prevent them from spreading and causing additional damage.

Dryer

As used herein, the term “dryer” refers to machines commonly used to dry clothing or other fabrics, including tumble dryers, even when used for other purposes. The dryer may be of any type normally manufactured and sold now or in the future and includes gas or electric dryers from household size to industrial or commercial scale dryers. As used herein, a dryer is not a hair dryer or other hand-held drying machine.

Almost all dryers contain ductwork associated with the dryer to vent hot air from the dryer, usually to the air outside the building. As used herein, the term “dryer” includes any associated ductwork, if present.

Temperature Sensor

In some aspects, the system includes at least one temperature sensor coupled to an alarm system. The temperature sensor coupled to an alarm system triggers an alarm state when the temperature inside the dryer exceeds a safe operating temperature. Some commercially available dryers include a temperature sensor for regulating the temperature of the drying chamber during operation, but which does not trigger an alarm if a safe operating temperature is exceeded. Some commercially available dryers include a thermocouple intended to shut down the dryer if a safe operating temperature is exceeded, but this is not a temperature sensor coupled to an alarm system.

The temperature sensor is positioned to measure the temperature inside the dryer or associated ductwork. In some aspects, the temperature sensor may be coupled to an alarm system and perform the dual function of regulating the temperature of the drying chamber and triggering the alarm state when the temperature inside the dryer exceeds a safe operating temperature. In such aspects, the temperature sensor is positioned to sense the temperature inside the drying chamber. In other aspects, the temperature sensor may be positioned to measure the temperature outside the drying chamber, but within the dryer machine or associated ductwork.

In some aspects, the temperature sensor coupled to an alarm system is independent from a temperature sensor that regulates the temperature of the drying chamber, if a temperature regulating sensor is present. In such aspects, the dryer system would include at least two temperature sensors, one of which regulates the dryer temperature during operation, and at least one of which is coupled to the alarm system. In such aspects, the temperature sensor coupled to an alarm system may be positioned, for example, to sense the temperature inside the drying chamber, and may be adjacent to or separate from the temperature sensor that regulates the temperature of the dryer during operation. In some aspects, the temperature sensor coupled to an alarm system is positioned outside the drying chamber, but positioned to measure the temperature within the dryer machine or associated ductwork.

In some aspects, the system includes more than one temperature sensor coupled to the alarm system. In some aspects having more than one temperature sensor coupled to the alarm system, one sensor may be the same as the temperature sensor for regulating the temperature of the drying chamber, which may be coupled to an alarm system and perform the dual function of regulating the temperature of the drying chamber and triggering the alarm state when the temperature inside the dryer exceeds a safe operating temperature. In some aspects having more than one temperature sensor coupled to the alarm system, one sensor may be positioned to measure the temperature inside the dryer chamber, and a second sensor to measure the temperature outside the dryer chamber, but within the dryer machine or associated ductwork.

Alarm System

The alarm system includes a processor, memory, input, and output. The alarm system receives a signal or reading from the at least one temperature sensor and determines whether the signal or reading is elevated enough to trigger an alarm state. The temperature reading necessary to trigger the alarm state may be set by the manufacturer and unable to be changed or may be able to be changed by a user. The temperature reading necessary to trigger the alarm state should be sufficiently high not to trigger an alarm state during normal operation of the dryer and should only trigger the alarm state when the temperature is high enough to pose a risk of fire. The temperature reading necessary to trigger the alarm state may differ depending on where the temperature sensor is mounted. For example, a sensor mounted to sense the temperature inside the dryer chamber would be expected to have a higher normal operating temperature than a sensor mounted elsewhere, such as in an exhaust duct.

In aspects having more than one temperature sensor, the temperature required to trigger the alarm state need not be the same for every temperature sensor. In aspects having more than one temperature sensor, an elevated reading from multiple sensors may be required to trigger the alarm state. In this way, the system can confirm that unsafe conditions are present by comparing readings from multiple temperature sensors or prevent false alarms caused by malfunctioning temperature sensors.

In some aspects, the alarm state triggered by the at least one temperature sensor coupled to an alarm system causes a signal to be output from the alarm system. In some aspects the output signal sets off an alarm. The alarm may be, for example, an audible alarm (such as a speaker), a visual alarm (such as a flashing light), or both. The alarm may be integrated with the dryer, may be remote (i.e. separate from the dryer), or both. When the alarm is remote, the output signal may be sent, for example, via an electrical cable to an audible or visual alarm.

In some aspects, the alarm system includes a data communication transmitter and/or receiver. The data communication transmitter and/or receiver may be wired or wireless. In such aspects, the alarm system transmits an output signal through the data communication transmitter using any known communications protocol through a communication network (such as the internet) to trigger an audible or visual alarm on an alarm connected to the communications network. The alarm connected to the communications network may be an independent device. The alarm may also be, for example, a program or application on a computer or handheld device capable of receiving the signal and capable of being triggered by the alarm system.

The alarm system may be integrated with the dryer or may be a separate system. When integrated, the alarm system is typically built into the dryer itself before the dryer is sold, and may, for example, include an alarm built into the dryer. Alternatively, the alarm system may be separate from the dryer, for example as an add-on system that is installed after the dryer is manufactured. When a separate system, the alarm system may be mounted inside the dryer, may be mounted to the outside of the dryer, or may be a completely separate self-contained unit.

In some aspects, the alarm system is coupled to the dryer's operating mechanism. In such aspects, when an alarm state is triggered the alarm system can deactivate the dryer or the dryer's heat source automatically or in response to a signal received by a user. In some aspects, the output signal from the alarm system automatically turns off the heat source used to heat the dryer. For example, if the dryer uses an electric heating element, the alarm state may cause the electricity to the heating element to be cut off. If the dryer uses a gas heating element, the alarm state may cause the source of gas to be cut off. In aspects where the alarm system deactivates the dryer in response to a user signal, after the alarm is triggered on the user's device, a signal may be received by the data communication receiver to deactivate the dryer in response to a user command.

Air Flow Sensor

Aspects of the system include an air flow sensor. The air flow sensor may be of any sort, such as an anemometer or other air flow sensor, that can be mounted inside the dryer duct and measure the air flow through the dryer duct.

The air flow sensor is positioned to measure the flow of air from the dryer or through the associated ductwork. The air flow sensor may be positioned at any location so long as it is capable of measuring the air flow at some point between the exhaust port of the dryer and the end of the dryer duct where the dryer vents to the air. The point where the dryer duct vents to the air is usually, but not necessarily, a vent in an exterior wall of the building where the dryer is housed. In some aspects, the air flow sensor is positioned to measure the air flow at the exhaust port of the dryer, where the dryer connects to the dryer duct. In some aspects, the air flow sensor is positioned to measure the air flow in the dryer duct where it connects to the dryer. In some aspects, the air flow sensor is positioned to measure the air flow in the dryer duct where it vents to the air. In some aspects, the air flow sensor is positioned to measure the air flow in the vent where the dryer duct vents to the air. In some aspects, the air flow sensor is positioned to measure the air flow in the dryer duct between the exhaust port of the dryer and the vent where the dryer duct vents to the air.

Without wishing to be bound by theory, when lint builds up in the dryer or the dryer exhaust network or ducting, the risk of fire increases. When lint build-up increases in the dryer exhaust network, the air speed changes because the air passing through the duct has less volume available to flow through. By measuring the air flow, readings from the air flow sensor can indicate whether the duct is becoming blocked by lint build-up and should be cleaned to prevent a fire.

In some aspects, the system includes more than one air flow sensor. In some aspects, the system may include, for example, two air flow sensors mounted at either end of the duct to determine if air flow is the same at the entry and at the exit.

In some aspects, the air flow sensor is coupled to the alarm system. In some aspects, the airflow sensor is coupled to a second alarm system. In either case, the alarm system receives signals or readings from the air flow sensor or sensors, and otherwise functions similarly to the alarm system coupled to the temperature sensor. The alarm system can be programmed to evaluate whether the air flow readings indicate a blockage in the dryer exhaust network that indicate a risk for a fire. When the readings from the air flow sensor or sensor indicate a risk for a fire, the alarm system can be programmed to output a signal triggering an alarm or warning that the dryer vent should be cleaned to remove lint build-up. The alarm system can send the output in all the same ways as in response to an elevated temperature reading, detailed above. The alarm system can be positioned in all the same ways as the alarm system coupled to the temperature sensor, described above.

Fire Suppression

Aspects of the invention include a fire suppression system. The fire suppression system is positioned to suppress or extinguish fires within the dryer or associated ductwork. Any sort of fire suppression system may be used so long as it may be positioned inside the dryer, in the dryer exhaust network, or in the dryer ductwork to extinguish fires before they spread. In some aspects, the fire suppression system is a powder fire suppression system. In some aspects, the fire suppression system is an inert gas fire suppression system. In some aspects, the fire suppression system is a fluid-based fire suppression system.

In some aspects, the fire suppression system is passively triggered, for example, by the heat of the fire itself. In some aspects, the fire suppression system is coupled to a sensor or sensors, such as a flame detector, smoke detector, or heat detector that detects the fire and triggers the fire suppression system. In some aspects, the sensors are coupled to the alarm system described previously. In such aspects, the alarm system may trigger the fire suppression system upon receiving a signal from the fire detection sensors.

The powder fire suppression system may include wet and/or dry chemical fire suppression agents, as well as solid aerosol particulate fire suppression agents, and may be of any type commonly used to extinguish small fires. For example, the powder fire suppression system may use sodium bicarbonate, also known as baking soda, as the powder. Sodium bicarbonate has the advantage of being inexpensive compared to other powder fire suppressants. Other useable materials include, for example, mono-ammonium phosphate, potassium bicarbonate, potassium carbonate, potassium nitrate. In some aspects, the powder is contained in a sealed bag or pouch that melts and releases the powder when a fire occurs. In other aspects, the powder may be discharged from a pressurized tank.

An inert gas fire suppression system may be of any type commonly used to suppress small fires, including nitrogen, carbon dioxide, argon, fluoroform, or helium gas. The principle of inert gas fire suppression would be to remove the oxygen from the area surrounding the fire, thereby extinguishing the fire.

Fluid-based fire suppression systems include water and non-water based fire suppression fluids. Non-water based fire suppression agents, like heptafluoropropane or fluorinated ketone, may be used to extinguish a fire that starts in the dryer. Non-water based fire suppression agents also include 2,2-dichloro-1,1,1-trifluoroethane fire suppression agents with or without inert gas propellants, such as found in HALOTRON I fire suppression agents. These non-water based fire suppression agents may be especially useful around electrical devices. For water-based systems, any water-based fire suppression system, such as a localized sprinkler system may be used and may include a self-contained reservoir or may be connected to plumbing to provide a water source. The water-based fire suppression system may only require a small volume of water and therefore would avoid damaging the surroundings if discharged.

EXAMPLES

Various experiments were performed to demonstrate the feasibility of the system.

First, the issue of overheating was examined. To test the use of temperature sensors at various locations in the dryer, the inventors repurposed a meat thermometer used for grilling as a temperature probe. The temperature probe could be placed at key locations in the dryer, and by adjusting the alarm temperature to go off at the maximum safe level for a dryer to work properly, the internal temperature of the dryer was monitored. For purposes of the experiment, a threshold below the operating temperature of the dryer was set. The temperature sensor was placed at various locations in the dryer and triggered an alarm when the temperature exceeded the threshold that was set for the experiment. Moreover, the temperature probe could be linked to a smartphone. When linked, the system sounded an audible alert at the dryer as well as sending a notice to the linked device, informing the operator that the safe operating temperature had been exceeded.

Second, the issue of lint building up in the dryer was investigated. Lint build-up is one of the leading causes of dryer fires. A tiny anemometer was installed at the external vent of the dryer, to monitor the normal air outflow rate of an unobstructed dryer. When installed, the anemometer produced a reading of the air flow rate when the dryer was operating. This experiment establishes that the air flow rate can be measured during operation. When lint builds up in the ducting and causes an obstruction the air flow will change. The anemometer could measure the air flow rate and a notification can be sent to the user through a linked smartphone, as described for the temperature sensor experiment above, informing the operator to clean out the lint build-up. The anemometer may also be installed in existing dryers and allow homeowners the benefits of a safer dryer without the expense of a new dryer.

Third, a prototype fire extinguishing system was created. Baking soda was used as an extinguishing powder because it is effective, inexpensive and readily available. The baking soda was contained in a thin plastic covering, similar in thickness to a medium weight sandwich bag, and attached to a metal backing using metal tape safe for high-heat applications. A model of a dryer vent was constructed and the extinguishing packet containing the baking soda was attached to the top interior of the vent model. A small lint fire was started inside the model, and the extinguishing packet melted open readily when heat from a small flame made contact with it, immediately dropping the power onto the flame and extinguishing it. This was repeated several times with similar results. 

1. A system comprising: a dryer; a temperature sensor positioned to measure the temperature inside the dryer or associated ductwork wherein the temperature sensor is coupled to an alarm system; an air flow sensor positioned to measure the air flow from the dryer or through associated ductwork; and a fire suppression system positioned to suppress fires within the dryer or associated ductwork.
 2. The system of claim 1, wherein more than one temperature sensor is coupled to the alarm system.
 3. The system of claim 1, wherein the alarm system is integrated with the dryer.
 4. The system of claim 1, wherein the alarm system comprises an audible alarm, a visible alarm, or both.
 5. The system of claim 1, wherein the alarm system comprises a wired or wireless data communications transmitter and/or receiver.
 6. The system of claim 1, wherein the alarm system is coupled to the dryer heat source.
 7. The system of claim 1, wherein the air flow sensor is coupled to the alarm system.
 8. The system of claim 1, wherein the fire suppression system is a powder fire suppression system, inert gas fire suppression system, or fluid-based fire suppression system.
 9. The system of claim 1, wherein the fire suppression system is passively triggered.
 10. The system of claim 1, wherein the fire suppression system further comprises a sensor.
 11. The system of claim 1, wherein the fire suppression system is a powder fire suppression system. 